1. Field of the Invention
The present invention relates to an electronic control circuit for the formation of a monostable switching behavior in a bistable relay, including a logic circuit for the conversion of binary input signals into control signals for a switching circuit through which the direction of current flow is reversible within the relay, whereby the relay is switchable at each status change of the input signal.
2. Discussion of the Prior Art
Control circuits of that type are presently known in the technology. Thus, for example, ascertainable from the data sheet of the SDS-Electro GMBH, pertaining to its module IC-12V, or IC-24V, is an electronic control circuit for a bistable relay by means of which there is produced a monostable switching behavior. Thereby, a bistable relay is connected in series with a condenser, wherein the condenser must be so dimensioned that the capacitance of the condenser produces a charging time constant in conjunction with the coil resistance of the relay which is at least as large as the response time of the relay. Obtained thereby, particularly in the control of relays with high switch rating pursuant to the second page of the data sheet, are capacitance values of up to a few hundred microfarads, which considerably increases the necessary volume for the control circuit.
The function of the control circuit is such that subsequent to the application of the control voltage, which must here be identical with the power supply for the relay is charged at one of the two control inputs of the above-mentioned condenser, and the relay is switched over with the charging current. When the control voltage drops out, then the condenser is discharged through a flip-flop which incorporates a transistor T5 as a power branch, and the relay is switched back into the initial condition by means of the discharge current of the condenser. This signifies that the relay will be switched over at each status change in the control voltage into the respective condition. When the condition of the relay is thus changed without any change in the status of the input voltage, due to disturbances, for example, of a mechanical type, then this is neither determined by the control circuit, nor is it corrected.
As has already been indicated hereinabove, the control voltage for the control circuit must concurrently supply the relay with power; in essence, any control of that type of control circuit with a usual logic transmission level is not possible, but a suitable power interface must be connected ahead thereof.
Furthermore, in the present circuit there is no provision to connect the relay in synchronism with a predetermined timing pulse, which is of particular advantage in the switching of alternating currents of high power (for example, switching during zero passage of the current cycle.)